Patent GB-707371-A (GB)
Title: Improvements in or relating to calculating machines
Inventor: EVANS DAVID SILVESTER
IPC: G06F7/57
Filed: 1949-01-07
Abstract: 707,371. Calculating-apparatus; transfer mechanism. ELLIOTT BROS. (LONDON), Ltd Jan. 6, 1950 [Jan. 7, 1949], No. 565/49. Class 106 (1) A binary calculator for the four rules of arithmetic comprises an accumulator consisting of a plurality of two-state elements identifiable with the digit places of a binary number, transfer means between each pair of elements rendered operative by each alternate change of state of the lower-value element to change the state of the higher-value element of a pair, means for conditioning the transfer means for either additive or subtractive operations, a register having a plurality of two-state devices identifiable with the digit places of a binary number, a plurality of means each associated with a digit place of the register and operable if the respective device is in its binary " 1 " setting to transmit a statechanging impulse from the associated digit place to that accumulator element of the same relative digit place, means for operating the impulsetransmitting means in sequence and allowing time for intermediate changes in the accumulator, counting means, and means adapted to change the counting means by one digit for each transmission of a sequence of state-changing impulses to the accumulator. In a first embodiment the two-state elements of the accumulator and the multiplier or quotient register each comprise a triode trigger pair V1, V2, Fig. 3. The L.H. side conducting condition represents digit " 1, " as indicated by illumination of a lamp 7, and can be entered by closing a push-switch 28: the element can be returned to zero by opening a switch 29. Normal entry from the input register or as a transfer from a lower digit place is by a negative pulse supplied at a terminal 22 which reverses the state of the trigger pair. Transfer to a higher digit place is made via a switch 25 which is settable for either additive or subtractive operation. In the upper (add) position a negative pulse is transmitted to the next higher digit place when the trigger pair changes from state " 1" to state " 0 ". In the lower (subtract) position a negative pulse is transmitted when the change is from " 0 " to "-1". Positive pulses arriving at a terminal 22 have no effect. Input.-Data is entered in binary form by setting two-position switches 6, Fig. 2, in accordance with the binary number to be entered. This number is subsequently read into the accumulator 2 as a sequence of pulses representing significant digits in ascending order, upon operation of a motor 30 which drives the arms of a multiposition switch 9. Alternate contacts of the lower switch bank are connected to a negative source so that when the arm 10 reaches a contact 12 which is connected to one of the closed switches 6 via the second arm 10a, the common condenser 13 supplies a negative pulse to the selected two-state element 20. In this way a succession of numbers can be added into the accumulator or, by employing a multi-contact switch 18 to perform denominational shifting, multiplication can be performed. The last contact 14a of the switch 9 is connected through the shifting device 18 to a multiplier register 3. Change over of devices 23, 23' transfers the contacts 25 to 27 (see Fig. 3) and provides for subtraction or division. In a second embodiment, Fig. 5 (not shown) electromagnetic relays are employed in place of the triode trigger pairs. In a third (mechanical) embodiment the accumulator comprises a plurality of discs 42, Fig. 6, having two positions of rest defined by stops 43, 44 which are urged into engagement with detents 48 by slipping clutches. The R.H. end of each detent 48 is urged into engagement with the edge of the lower disc by a spring 50 and co-operates with a notch 42a when set for additive operation. A binary entry is made by setting triggers 5' in accordance with the number to be added. Subsequent longitudinal displacement of the shaft 40 carrying the triggers brings those triggers which have been set in the " 1 " position into engagement with the lower ends of latch arms 51 in succession, releasing the associated discs to allow a 180 degrees movement in each case. Where this movement is from the " 1 " to the " 0 " position the notch 42a allows the associated detent 48 to release the next higher disc for a 180 degrees movement in the brief interval before entry by the trigger 5' for that place is due to occur. For subtractive operation the detents are all moved to co-operate with axially displaced notches 42b opposite notches 42a. For multiplication or division, repeated operation of the input shaft 40 is registered on a counter 52 via pawl- and-ratchet means.